The new French restaurant in the River North neighborhood simply announced on Wednesday that a surprise guest would take the stage at its newly-opened upstairs club, Studio Paris, later that night. No clues were given until hours before the performance when co-owner R.J. Melman tweeted a photo of a microphone with the caption “Who's voice will be singing on this mic @StudioParisChi tonight?”

It wasn’t until the 300 or so VIP guests arrived — including the White Sox’s Gordon Beckham, Mark Teahen and Brent Morel and Sacramento Kings co-owner George Maloof Jr. — that most learned about the surprise performer’s identity.

“We wanted a fun surprise for our guests that were there that night,” Melman said by email. “Expect this a sign of things to come at Studio Paris.”

Green kicked off his six-song set with “Bright Lights Bigger City” and ended with the explicit version of “Forget You” before relaxing with his entourage, including Goodie Mob rapper Big Gipp, until closing.

The 37-year-old artist recently wrapped up filming of the first season of NBC’s hit reality show “The Voice” and has signed on for the second season (Chicago auditions take place at Navy Pier Friday and Saturday). Green also reportedly has been offered a judge position with the British version of the singing competition.

“They asked me not to speak about it,” Green told me while sitting in his booth. “It’s not official yet.”

Did Green expect the U.S. version to perform as well as it did in the ratings?

“When you do something for the first time, it’s awkward and unfamiliar,” said Green, who is set to perform at Lollapalooza Aug. 6 and Macy’s Glamorama at the Chicago Theatre Aug. 13. “But I thought it was a great idea on paper. I felt like, ‘This sounds promising. Let’s give it a shot.’”